CN1176032C - Producing process and technology for electronic grade water by intergrated film process - Google Patents

Abstract

An integrated membrane process production method for electronic grade water, using tap water as raw water, sequentially undergoing four components: pretreatment, primary pure water system, secondary pure water system and terminal membrane filtration fine treatment to obtain electronic grade ultra-pure water. Among them, the pretreatment unit mainly includes sand filtration, ultrafiltration, activated carbon adsorption and nanofiltration. The primary pure water system is mainly composed of reverse osmosis, membrane degassing, electrodeionization, boron selective ion exchange resin and other units. The water system is mainly composed of UV lamp oxidation and polished mixed bed resin, and the terminal membrane filtration is treated with polished reverse osmosis membrane. The water production system can realize efficient, clean and reliable non-chemical regeneration ultrapure water production, does not discharge environmentally harmful wastewater, and can effectively remove impurity boron, reduce the cost of the water production system, and improve water utilization. Terminal filtering is safer and more reliable.

Description

A membrane-integrated process production method for electronic grade water

Technical field

The invention relates to a method for producing ultrapure water, in particular to a method for producing electronic-grade ultrapure water through an integrated membrane process.

Background technique

The ultrapure water referred to in the present invention refers to the removal of various suspended impurities, inorganic ions and non-ionized impurities in water, including various organic substances, microorganisms such as bacteria and viruses, and fine particles, etc. to the limit value that can be achieved. "Deionized Water" or "High Resistivity Water" or "Ultra High Purity Water".

The national standard GB/T 11446.1-1997 defines "electronic grade water" as "high-purity water used in the process of manufacturing electronic components". The highest grade of electronics grade water is wash water used in very large scale and very large scale integrated circuit production. The electronic industry's quality requirements for ultra-pure water are different from all other industrial sectors and need to consider all pollutants in the water.

As a part of the integrated circuit production environment, pure water has a great impact on product quality. In nearly every processing step, layers of conductive or insulating material are added to the surface of the silicon wafer. Parts of the surface are etched away with aggressive chemical acids before the next layer is applied. Therefore, in order to ensure thorough rinsing and removal of chemicals on the surface of silicon wafers, it is necessary to use pure water to clean the product. However, trace impurities in the pure water used in the process may recontaminate the product. Therefore, the quality of pure water has a crucial impact on the production quality and production cost of integrated circuits.

When the semiconductor industry first came out in the late 1950s, the resistivity of 18MΩ·cm (25°C) was considered the only water quality indicator for ultrapure water, and the deep deionization technology at that time - ion exchange was sometimes able to produce Produce ultrapure water with a resistivity of 18MΩ·cm. Later, it was gradually found that it was far from enough to measure the quality of product water with only one index of resistivity. In the mid-1970s, five new indicators of particles, bacteria, carbon dioxide, sodium, and total organic carbon (TOC) were proposed, and the process of water production began to use a combination of reverse osmosis and ion exchange. In the 1980s, the control of particulates and bacteria became more and more stringent, and ultrafiltration technology was introduced into the production of electronic grade water accordingly, and in addition, the limit index of dissolved oxygen was increased. In the 1990s, it has entered the ULSI era, and all countries are constantly exploring new ultrapure water manufacturing systems suitable for the production of megabit-level integrated circuits. Therefore, the continuous improvement of integrated circuit integration has made the requirements for pollutants in pure water increasingly stringent, and ULSI's requirements for pure water quality have become the extreme value of contemporary ultrapure water quality.

Table 1 shows the technical indicators of Japan's ultrapure water for integrated circuit production with 64M DRAM integration and China's "electronic grade water" national standard GB/T 11446.1-1997 EW-I grade water.

Table 1. Electronic grade water quality standards project Japan IC pure water quality standard integration degree 64M, line width 0.35μm GB/T 11446.1-1997 EW-I Resistivity (MΩ·cm, 25°C) >18.2 >18 (95% of the time), not less than 17 Microparticles (pcs/mL) > 1μm > 0.05μm > 0.03μm <1<10 <0.1 Bacteria (unit/mL) <0.001 <0.01 TOC (ppb) <1 <20 SiO ₂ (ppb) <0.1 <2 Na(ppb) <0.01 <0.5 Ni(ppb) <0.1 K <0.5 Fe(ppb) <0.01 Zn(ppb) <0.01 <0.2 Cu(ppb) <0.01 <0.2 Cl ^- (ppb) <1 NO ₃ ^- (ppb) <1 PO ₄ ^3- <1 SO ₄ ^2- <1 Amide (ppb) <0.01 Dissolved oxygen DO(ppb) <5

For the production of electronic grade water, the removal of weakly ionized silicon (SiO _{2 ,} etc.), boron, (B), and dissolved carbon dioxide (CO ₂ ) among the required inorganic impurities has always been a difficult problem in water treatment technology, especially Silicon and boron are more difficult to remove.

Silicon, especially soluble silicate ions, in addition to affecting pattern defects, can also cause phosphorous silicon fog and threshold voltage changes. The content of boron in ultrapure water is generally not paid attention to by people, but the progress of analytical science in recent years has made people realize that the trace amount of boron contained in ultrapure water is another important impurity species that affects the quality of semiconductor processing. The boron concentration in the lattice substrate has a decisive influence on the threshold voltage of the multi-channel transistor generated based on the substrate, so the higher concentration of boron in the ultrapure water used for cleaning will make the boron concentration in the substrate difficult to control, resulting in product defects. In addition, when fine multi-channel transistors are used to produce high-integration semiconductor products, such a fine product production process requires that the boron concentration in the substrate along the thickness direction can be precisely controlled, which in turn requires the production process. The boron concentration in the ultrapure water used has a rather low value.

The traditional pure water preparation technology generally contains at least three units of pretreatment, desalination, and non-ionized impurities, but generally has two obvious shortcomings. One is that the equipment investment and operation and maintenance costs remain high; the other is that a large number of environmentally hazardous waste liquids are dealt with and discharged, which is mainly caused by the use of ion exchange resins that require chemical regeneration. The use of ion exchange technology not only leads to low production efficiency, complicated operation, and uncontinuous operation of the system due to the consumption of a large amount of acid and alkali to regenerate resin, but also the main problem is that a large amount of waste acid and lye is difficult to handle and seriously pollutes the environment. In recent years, pure water production technology without any chemical regeneration has attracted much attention, and traditional ion exchange is being replaced by technologies such as reverse osmosis (RO) and electrodeionization (EDI). These new pure water preparation technologies generally take the membrane separation process as the technical core, combined with other pre- and post-treatment methods to form an integrated membrane process to meet production requirements. The use of technologies such as RO and EDI has largely solved the problems of low efficiency of the water system and the generation of environmentally harmful wastewater.

Patent JP 11244853A2 has designed the following technological process for the cleaning water required in the production process of semiconductors, optical lenses and liquid crystals. Firstly, adjust the pH value of the pretreated tap water to 4-5, and then go through the first-stage reverse osmosis desalination and degassing unit to remove dissolved carbon dioxide and other gases, and then re-adjust the pH value to 7-11 before entering the second-stage reverse osmosis. Osmotic desalination, the product water of the secondary reverse osmosis is further deionized by electrodeionization to obtain ultrapure water.

The design of the patent JP 11244854A2 first adjusts the pH value of the pretreated tap water to 8-11, and then obtains ultrapure water through the first-stage reverse osmosis and electrodeionization processes. The concentrated water of the first-stage reverse osmosis enters another reverse osmosis unit, and its concentrated water is discharged, and the desalinated water and the concentrated water of EDI are recycled to the feed water of the first-stage reverse osmosis to improve water utilization.

Patent JP 11262771A2 also adopts the process design with "reverse osmosis/electrodeionization" as the core, but the pretreatment method is relatively complicated. First, adjust the pH value of the raw water to 3-5 for degassing, then use anion exchange resin to absorb organic matter, then adjust the pH value of the water to 6-9.5 and enter the downstream "reverse osmosis/electrodeionization" system to obtain ultrapure water .

However, the existing pure water and ultrapure water preparation technologies are still difficult to balance the water purity and the economy and efficiency of the water production process; in addition, the latest developments in analytical science have also brought new opportunities for the preparation of electronic grade ultrapure water. new problems and problems. This is mainly manifested in the following aspects:

1. Cannot effectively remove boron

Raw water used for ultrapure water production, such as tap water, well water or river water, generally has a boron concentration of tens of ppb, and the existing ultrapure water production processes are difficult to ideally remove this low concentration of trace boron. For the ion exchange process that adopts chemical regeneration, the weakly dissociative boron will leak from the bed within a short time of operation, so the boron concentration in the product water can only be controlled by increasing the regeneration frequency of the ion exchange resin bed. In addition, RO and EDI, which have been widely used, can only remove about 40% and 75% of boron, respectively. For the production process using "two-stage reverse osmosis-mixed bed ion exchange" and "reverse osmosis-electrodeionization" deep desalination, the product water after the terminal membrane filtration will still contain 3-10ppb boron, and this concentration Levels are still too high.

Second, the equipment investment of the first-level pure water system is too high, and the water utilization rate is low

For the current ultrapure water production process, the design of two-stage reverse osmosis plus ion exchange (or EDI) is generally used in the primary pure water system. Although the two-stage reverse osmosis can greatly reduce the burden on the subsequent ion exchange column, the investment cost of the system is too high, and the water utilization rate of the water production system is low. Generally, the total water utilization rate of two-stage reverse osmosis does not exceed 35%.

3. Terminal fine treatment still cannot fully meet the requirements

When the photolithographic line width is reduced to below 1 μm, an ultrafiltration membrane is generally used for terminal filtration. At present, the terminal treatment method of 0.1 μm UF-UV (ultraviolet light)-0.04 μm UF is mostly used, but for the production of integrated circuits with an integration level exceeding 64 MDRAM, it is still impossible to ensure that the indicators such as particles in the product water are qualified.

Therefore, for the preparation of the most complicated electronic grade water, it is necessary to adopt a more scientific and reasonable comprehensive integrated process, which can completely remove various organic and inorganic impurities in the water, and produce qualified ultrapure water reliably and safely. Reduce system investment costs and improve water resource utilization.

Contents of Invention

The purpose of the present invention is to address the shortcomings of the existing ultrapure water production technology, to provide a new integrated membrane process that combines various membrane separation processes and other water treatment processes, to effectively remove various impurities in water, and to achieve high efficiency, Clean and reliable non-chemical regeneration ultrapure water production is not only notable for eliminating the problem of environmentally hazardous wastewater treatment, but also has higher water production efficiency, more reliable system operation, and can more effectively remove impurity boron and produce The water utilization rate of the water system is improved, and the terminal filtration is safer and more reliable.

The purpose of the present invention is achieved through the following technical solutions:

Design a simultaneous integration of ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), electrodeionization (EDI), membrane degassing, polished reverse osmosis (PRO) and other membrane separation processes and sand filtration , activated carbon adsorption, pH adjustment, ultraviolet irradiation, polished mixed bed ion exchange and other processes combined integrated membrane process, the process includes a pretreatment unit, a primary pure water system (including boron removal unit), a secondary pure water system, The terminal fine processing unit has four components. City tap water is used as raw water, and through the above four treatment steps in sequence, electronic grade ultrapure water is finally obtained.

(1) Preprocessing unit

The preprocessing unit adopts the process design with "UF-NF" joint as the core.

UF is a membrane separation process that uses pressure as the driving force to separate liquids by physical sieving. The operating pressure is usually 0.2-0.3 MPa. The UF membrane that can be used in the present invention can be a UF membrane of organic polymer material or inorganic material. Organic material UF membranes mainly include polysulfone and polyolefin membranes, such as polysulfone (PS), sulfonated polysulfone (SPS), polyethersulfone (PES), polypropylene (PP), polyacrylonitrile (PAN), etc.; The inorganic material UF membrane is mainly an inorganic ceramic membrane. For the UF membrane used in the present invention, the molecular weight cut-off is controlled to be 20,000-50,000.

Using urban tap water as raw water, separated by UF membrane, can remove colloids, particles, macromolecular organic matter, bacteria and other impurities in the raw water, reducing the pollution index of the raw water to below 3.

NF is also a membrane separation process that uses pressure as the driving force and uses physical sieving to separate liquids. The pore size ranges from 1 to 3 nanometers, and the average pore size is 2 nanometers. The membrane pore size, operating pressure and separation performance of NF are between RO and UF. The main types of NF membranes that can be used are cellulose acetate-triacetate cellulose (CA-CTA) membranes, aromatic polyamide composite membranes and sulfonated polyethersulfone membranes. The rejection rate of NF membrane for monovalent ions is less than 20%, and for calcium, magnesium hardness ions and other divalent and high-valent ions, the removal rate can reach more than 95%, and the salt removal rate can reach 50-70%. In addition, the removal rate of NF to various organic impurities with a molecular weight above 200 can also reach above 90%. The NF membrane grades that can be used include ESNA1-4040, ESNA1, etc., and the operating pressure is about 0.5MPa. For multi-branch and large-scale NF membrane systems, the water recovery rate of the system can be as high as 85% through reasonable design of the process.

The use of NF membrane softening between UF and RO can prevent downstream RO membrane fouling and reduce organic impurity pollution in downstream processes.

An activated carbon adsorption filter is set between UF and NF to further adsorb and remove microorganisms such as organic matter and bacteria and viruses, and reduce the burden of organic pollution on the NF membrane.

A security filter using a honeycomb filter element is set between the activated carbon adsorption filter and the NF to prevent activated carbon powder from entering the downstream NF membrane module. The filter pore size of security filter is 1-5μm.

If the raw water quality deviates, depending on the specific water quality, install quartz sand filters, mechanical filtration and other devices before UF to strengthen pretreatment, so as to remove suspended solids, large particles and other impurities in the water and reduce turbidity, preventing UF membrane The pores are clogged and the flux drops. The used sand filter has a filter medium of 0.4-1.0 quartz sand.

(2) Primary pure water system

The primary pure water system includes pH adjustment, primary RO, ozone sterilization, membrane degassing, deep desalination unit and boron removal unit in sequence.

The raw water pretreated by "UF-NF" can avoid scaling in the downstream RO membrane components because most of the hardness ions have been removed. Before the water enters the first-stage RO membrane module, the pH value of the water is adjusted to a weak alkaline of 8.0-11.0 by adding dilute NaOH solution, etc., and the pH value is preferably 9.0-10.0, which is conducive to the dissolution of CO ₂ , TOC, Sufficient removal of _SiO2 , and ultrapure water with high resistivity through EDI unit after RO. After pH adjustment, the NF water is desalinated by one-stage RO, and the conductivity of the product water reaches 1-5μs/cm. At the same time, the RO membrane can further remove residual organic matter, bacteria, and particles. For the present invention, the RO membrane used is a low-pressure polyamide composite (TFC) membrane with a high desalination rate (greater than 99%), and the commercial RO membrane grades that can be selected include CPA-ULTRAPURE, CPA-3, CPA-4, ESPA- ULTRAPURE, etc., its standard operating pressure is 1.05-1.55MPa.

The pure water obtained through the first-stage RO enters the first-stage pure water tank, and the water tank is filled with nitrogen to protect the pure water from secondary pollution by impurities such as particles in the air and carbon dioxide. In addition, an on-site ozone generator is used to add ozone with a concentration of 0.1-0.3ppm to the pure water tank to prevent bacterial growth.

The primary RO pure water enters the hollow fiber membrane degassing module through the pure water pump to remove dissolved oxygen in the water. The component adopts RO membrane made of hydrophobic TEFLON or PE, which can only pass through gas or oxygen. The pure water passes through the hollow fiber, and the dissolved oxygen permeates to the outside of the membrane, and the residual dissolved oxygen concentration in the water is reduced to below 5ppb by nitrogen purging. In addition to removing dissolved oxygen, the membrane degasser can also remove residual dissolved carbon dioxide to reduce the burden on the downstream resin.

The EDI deep desalination device used in the present invention is a new deep desalination means that has been rapidly popularized and used in recent years. Its technical feature is to fill the fresh water chamber of the electrodialyzer with increased thickness. bed ion exchange resin, which combines electrodialysis and ion exchange, demineralizes deeply through electric energy and ion exchange resin and membrane, and at the same time realizes continuous regeneration of resin through electric energy, eliminating the need for frequent regeneration of acid and alkali on ion exchange resin and direct , Continuously produce ultrapure water with a resistivity of 16-18MΩ·cm.

For the present invention, after the raw water is treated by UF, NF, RO and other membrane processes, it is further desalinated by EDI. Compared with the traditional chemical regeneration or non-regeneration mixed bed ion exchange bed, there is no need for complex regeneration or regeneration of the resin. Change resin frequently. In addition, EDI also has the ability to remove dissolved carbon dioxide, silicon dioxide, boron and other impurities without pH adjustment, and has the ability to inhibit and kill bacteria. The weak alkaline pH adjustment prior to RO, as well as the H ⁺ and OH ^- ions generated by the characteristic water dissociation in the EDI process, contribute to the ionization of these weakly dissociative impurities. This ionization in the EDI process is that in the fresh water chamber of EDI, the dissociation of water occurs on the surface of the ion exchange membrane and ion exchange resin, and the water molecules are dissociated into H ⁺ and OH ^- ions, and some OH ^- The ions are combined with weakly ionized silicon and boron impurities in water to generate silicate and borate ions respectively, which are removed from the freshwater flow through the resin and membrane under the action of an external DC electric field. The EDI device used in the present invention has been specifically described in the patent ZL00200207.8.

The boron removal unit passes pure water through an ion exchange resin column filled with boron selective adsorption. The resin used in the resin column is different from the strong basic anion exchange resin used in the general ultrapure water production process. The active functional group of the ion exchange is polyhydric alcohol, which belongs to the weak basic anion resin. Containing this kind of weakly basic ion exchange resin with polyhydric alcohol as the exchange functional group can remove trace boron in water very effectively and stably, ensuring that the boron content in the effluent is lower than 0.01-0.1ppb.

In the water production process, the boron selective resin is installed after the EDI deep desalination to completely remove the trace amount of boron involved in the EDI product water, protect and improve the water quality. In the present invention, the boron-selective ion-exchange column is designed as a non-regenerating type to avoid contamination by Cl ^- , OH ^- and other anions during chemical regeneration. The resin is replaced directly after adsorption saturation.

(3) Secondary pure water system

The secondary pure water system sequentially includes an ultrapure water tank, an ultraviolet lamp oxidizer and a polished mixed bed ion exchange.

Both the ultrapure water tank and the polished mixed-bed ion exchange column are protected by high-purity nitrogen. The ultraviolet oxidizer uses a low-pressure 185nm ultraviolet lamp to decompose a very small amount of TOC components remaining in the primary pure water system, especially suitable for decomposing low-molecular-weight organics with a low removal rate in the RO membrane, and further reducing TOC to below 1ppb. The polished mixed bed selects low-elution uniform particle ion exchange resin to remove the small molecular organic matter and CO ₂ produced by the decomposition of TOC by the pre-ultraviolet oxidizer. highest level reached. The average particle size resin used is defined as the particle size of 95% of the anion and cation exchange resin particles is within 10% of the average particle size. The polishing mixed bed is designed as a non-regenerative mixed bed to avoid secondary pollution during regeneration, and the resin is replaced directly on a regular basis.

(4) terminal membrane filtration

Ultra-low pressure polished composite reverse osmosis membrane (PRO) with a molecular weight cut-off of 100 is used as terminal filtration instead of conventional ultrafiltration, and the cut-off particle size is 0.0001 μm, which can completely remove trace TOC, particles, bacteria and other impurities that may be produced in the upstream polishing mixed bed , to ensure that the water quality of the product meets the water requirements of integrated circuits with a lithographic line width of 0.13 μm or even smaller.

The integration of each component in the present invention can produce the following effects:

UF-activated carbon-NF joint pretreatment can remove various colloids, particles, organic matter, bacteria and other impurities in water, as well as calcium and magnesium hardness ions and 50-70% of salt, to prevent downstream RO membrane scaling and ensure its Service life; units such as RO, membrane degassing, EDI deep desalination and boron selective resin in the primary pure water system can efficiently and continuously remove microorganisms such as inorganic ions, boron, silicon, dissolved oxygen and bacteria in the water, and the effluent The resistivity reaches 16-18MΩ·cm; the ultraviolet lamp oxidizer and polishing mixed bed in the secondary pure water system completely remove traces of low molecular weight organic matter, bacteria and ionic impurities remaining in the system; the terminal polished reverse osmosis membrane filter completely removes the measurement particles, TOC and bacteria, and finally obtain ultra-high purity electronic grade water.

Description of drawings

Fig. 1 is the production process block diagram of electronic grade ultrapure water provided by the present invention;

Detailed ways

In the process flow shown in Figure 1, sand filter-ultrafiltration-activated carbon-safety filtration-nanofiltration pretreatment removes suspended solids, particles, pigments, turbidity, organic matter, colloids, microorganisms, calcium, magnesium hardness ions and 50 -70% salt content, among which polyethersulfone ultrafiltration membrane with a molecular weight cut-off of 20,000-50,000 is used for ultrafiltration, and aromatic polyamide ESNA1 membrane is used for nanofiltration. Reverse osmosis removes ionic and non-ionic (organic, particulate, etc.) impurities from pretreated water. If necessary, adjust the pH between NF and RO, and adjust the pH value of the RO feedwater to be weakly alkaline, such as pH 9.5, so as to effectively remove TOC, CO ₂ and SiO ₂ . The RO membrane used is an aromatic polyamide CPA-ULTRAPURE membrane.

The reverse osmosis pure water tank is protected with nitrogen to avoid secondary pollution from the air. In addition, the tank is filled with the right concentration of ozone produced on site to prevent bacterial growth. Membrane degassing unit is used to remove residual oxygen, nitrogen and carbon dioxide from water. The electrodeionization unit continuously desalinates in depth, avoids repeated regeneration of resin by chemicals, does not discharge polluting waste water, and makes the effluent resistivity reach 16-18MΩ·cm. The exchange column filled with boron-selective ion-exchange resin is placed downstream of the electrodeionization unit to completely remove trace amounts of boron in the water, so that the boron concentration in the product water is lower than 0.01ppb to obtain first-grade pure water. In addition to protecting the resin column with nitrogen, the available boron-selective resin grades include AMBERLITEIRA-743T from Rome & Hass and DIAION CRB02 from Mitsubishi Chemical Industries.

The ultrapure water produced by the first-level pure water system enters the second-level pure water system, and successively passes through the ultrapure water tank, ultraviolet oxidation, polishing mixed bed resin to improve water quality and terminal polishing reverse osmosis treatment, and the product water is supplied to the ultrapure water water point. The UV lamp oxidizer used has an ultraviolet wavelength of 185nm, which is used to decompose the residual low molecular weight organic matter in the primary pure water system. The polished mixed bed can remove measured small molecular organic matter and CO ₂ , and further increase the resistivity of the effluent. The polishing mixed bed is also filled with nitrogen protection. Polished reverse osmosis is used as the ultimate water quality protection method to completely remove fine particles, bacteria and residual TOC.

Therefore, the ultrapure water production process provided in Figure 1 does not contain any chemically regenerated deionization units, and can run continuously for a long time to produce boron-free ultrapure water without generating any environmentally hazardous waste liquid. Compared with the design of "two-stage reverse osmosis-electrodeionization" or "two-stage reverse osmosis-ion exchange mixed bed", not only the equipment investment is reduced, but the water utilization rate is improved, and it can stably and efficiently remove the integrated circuit Trace amounts of boron are unfavorable for production.

In the production process provided in Figure 1, the pipeline of the pretreatment part is made of clean polyvinyl chloride (C-PVC), polypropylene (PP) or ABS, and the reverse osmosis part of the nanofiltration and primary pure water system uses Stainless steel or polished stainless steel pipes, the pipes from reverse osmosis to the terminal water point are all made of standard polyvinylidene fluoride (PVDF) or high-purity PVDF (PVDF-HP) or Teflon (PFA). When the production line is used to provide warm ultrapure water, the corresponding pipelines are only made of PVDF-HP or PFA. PVDF and PFA are far superior to PVC, PP and ABS in terms of chemical stability and maximum working temperature, and have no additives and no leachable substances, so bacteria cannot survive, so their bacteria and TOC indicators are very low and will not cause Decrease in product water resistivity.

Claims (7)

1, a kind of integrated membrane process production method of electronic grade water, with city tap-water is former water, make the electronic-grade ultrapure water through pre-treatment, one-level pure water system, secondary pure water system and four integral parts of terminal membrane filtration precision processing successively, it is characterized in that making the water process and take following integrated membrane process technology:

(1) adopt " sand filtration-ultrafiltration-gac-security personnel's filtration-nanofiltration " integrating process to form pretreatment system;

(2) adopt " pH regulator-reverse osmosis-ozone sterilization-film degassing-electrodeionization-boron selective ion exchange resin " integrating process to form the one-level pure water system, and to fill with the high pure nitrogen in reverse osmosis water tank, boron selective ion exchange resin column and one-level ultrapure water water tank be to protect gas;

(3) adopt " ultraviolet lamp oxidizer-polishing mixed bed ion exchange " to form secondary pure water system, and to fill with the high pure nitrogen in polishing mixed-bed resin post be to protect gas;

(4) adopt " polishing reverse osmosis " as the terminal membrane filtration system.

2, the integrated membrane process production method of electronic grade water according to claim 1 is characterized in that, the filtration medium of employed sand-bed filter is the quartz sand of 0.4-1.0mm in the pre-treatment.

3, the integrated membrane process production method of electronic grade water according to claim 1 is characterized in that, the adjusting of between nanofiltration and reverse osmosis the pH value of water being carried out is to add dilute NaOH solution to make the water inlet pH value of reverse osmosis be 8.0-11.0.

4, the integrated membrane process production method of electronic grade water according to claim 1, it is characterized in that, employed ultra-filtration membrane in the pre-treatment, be that molecular weight cut-off is 20,000-50,000 organic polymer material ultra-filtration membrane or inorganic ceramic ultra-filtration membrane, the material of organic polymer ultra-filtration membrane wherein is a kind of in polysulfones or SPSF, polyethersulfone, polypropylene and the polyacrylonitrile.

5, the integrated membrane process production method of electronic grade water according to claim 1, it is characterized in that, employed nanofiltration membrane in the pre-treatment, its pore diameter range is the 1-3 nanometer, its material is cellulose acetate-cellulosetri-acetate, or a kind of in aromatic polyamides and the sulfonated polyether sulfone.

6, the integrated membrane process production method of electronic grade water according to claim 1, it is characterized in that, employed reverse osmosis membrane in the one-level pure water system is standard operation pressure 1.05-1.55MPa, and ratio of desalinization is greater than 99% low pressure polyamide composite reverse osmosis membrane.

7, the integrated membrane process production method of electronic grade water according to claim 1 is characterized in that, the polishing reverse osmosis membrane that end-filtration is used, and for holding back size of particles 0.0001 μ m, molecular weight cut-off is 100 ultralow pressure complex reverse osmosis membrane.

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